JPH05210301A - Developing method - Google Patents

Abstract

PURPOSE:To provide a new developing method without a difficulty even in the case of using developer obtained by mixing carrier particles which are particulate, expressly desirably magnetic carrier particles with toner particles. CONSTITUTION:This method is constituted of a stage where the developer D principally composed of the toner particle whose average particle size is <=20mmu and the insulating magnetic carrier particle whose average particle size is 5-50mmu is carried to a developing area while continuously forming a developer layer on a developer carrier 2 consisting of a magnet arranged inside and a sleeve 2a surrounding the magnet by the action of magnetic force, and a stage where the developing area is formed as a gap between an image carrier 1 and the developer carrier 2, oscillating electric field is formed in the developing area, a distance between the image carrier 1 and the developer carrier 2 in the developing area is larger than the thickness of the developer layer, and the toner T in the developer is moved and stuck on the image carrier 1 in the developing area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for developing an electrostatic image, in which an electrostatic image formed on an image carrier of an electrostatic recording device such as an electrophotographic copying machine is made visible, or a magnetic image is made visible. The present invention relates to a method for developing a magnetic image to be an image.

[0002]

2. Description of the Related Art First, as an example, an outline of a copying process in an electrophotographic copying apparatus will be described. For example, in the fixed document table type, a copy document is placed on the document table, and when a copy button is pressed, the exposure lamp irradiates the document while performing exposure scanning in a predetermined relationship with an optical system having a reflection mirror or the like. Reflected light corresponding to the lightness and darkness of the original is irradiated onto the uniformly charged image carrier (photosensitive drum) via the optical system, and an electrostatic image is formed on the photosensitive drum. And this electrostatic image is
The image is developed by the developing device and becomes a visible image with toner corresponding to the density of the original.

On the other hand, a copy sheet (transfer material) is sent from a sheet feeding device in synchronization with the rotation of the photoconductor and overlaps with it so as to coincide with the toner image formed on the photoconductor, and then transferred to the copy sheet by a transfer electrode. To be done. The copy paper on which the toner image is transferred is separated from the photoconductor and sent to the roller fixing device. The roller fixing device is composed of two rollers, at least one of which is a heated roller, heat-fixes the toner image transferred to the copy paper, and then the copy paper is discharged to the outside of the copying apparatus main body. ..

By the way, as the developer, there are a two-component developer and a one-component developer. The two-component developer is
It is composed of a toner which is a colored particle and a carrier which is necessary to charge the toner or to convey the toner to a developing unit. On the other hand, the one-component developer is mainly composed of colored particles in which a resin and a magnetic material are integrally formed. A magnetic brush developing method is generally known as a developing method using a developer containing a magnetic material.

Next, the outline of the magnetic brush developing method will be described. A developer carrying carrier containing a fixed or rotatable magnet roll is provided in the vicinity of the photoconductor. The developer is brought into sufficient contact with a part of the developer transport carrier, and when one or both of the magnet roll and the developer transport carrier are rotated, the developer spikes are formed on the peripheral surface of the sleeve, The developer is conveyed, and the developer comes into contact with the photoconductor in the developing section, so that the toner particles are attracted to the charged portion of the photoconductor and a visible image is formed on the photoconductor by the toner particles.

The magnetic brush development method using a one-component developer has the drawback that toner particles are less likely to be charged due to friction and aggregation of the toner particles is likely to occur. Therefore, the toner particles are sufficiently charged on the charged portion of the photoreceptor. May not be aspirated. However, when the two-component developer is used, the above-mentioned harmful effects do not occur, and the sharpness of the magnetic brush is good,
Since it has features such as excellent rubbing properties with the photoconductor,
It is widely adopted.

However, in this developing method, since toner particles and carrier particles of a developer generally used in the past are coarse, it is difficult to obtain a high-quality image in which delicate lines or dots, or differences in density are difficult to obtain. There is. In order to solve this problem, resin coating of carrier particles,
Although improvements have been made to the magnet roll built in the developer transport carrier and the application of a bias voltage to the developer transport carrier, the actual situation is that a satisfactory image cannot be obtained yet.

In order to record a high quality image, it is necessary to make toner particles and carrier particles fine particles. However, making the particles finer causes the following problems. Generally, the charge amount of particles is proportional to the square of the particle size, and if the toner particles are 20 μm or less, especially 10 μm or less, the charge amount of one toner particle due to friction becomes small, so that van der Waals that acts on the particles is reduced. The power becomes relatively large.

Due to the above-mentioned two problems associated with making the toner particles into fine particles, it has been impossible to use fine toner particles in the magnetic brush developing method. That is, when the toner particles are made into fine particles, the charge amount of the toner particles does not become sufficiently high due to friction, and even if the toner particles come into contact with the photoconductor in the developing portion, they are not significantly affected by the electric force of the charged portion of the photoconductor and the charging is performed. It becomes difficult to be sucked into the part. And because the van der Waals force becomes relatively large,
Toner particles adhere to the non-charged portion of the photoconductor in the developing section, causing so-called fog that marks the recording of the background portion of the image background, which can also be prevented by applying a bias voltage to the developer carrier. Becomes difficult. Further, since the van der Waals force is increased, the toner particles are likely to aggregate.

On the other hand, when the carrier particles are particularly fine particles of 50 μm or less, the carrier particles are also less susceptible to the influence of the magnet roll of the developer carrying carrier, and are not separated from the toner particles by Coulomb force or Van der Waals force. It'll be easy. Due to these, the carrier particles are also attracted to the photoconductor together with the toner particles. If the toner particles and the carrier particles are made into fine particles, the above-mentioned problems occur, and it is not possible to record a clear image. Therefore, in the magnetic brush developing method, it was not possible to use the fine particle toner and the carrier.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a new developing method without the above-mentioned obstacles even when a developer in which fine particle carrier particles, particularly preferably magnetic carrier particles and toner particles are mixed is used. Is intended to provide.

[0012]

DISCLOSURE OF THE INVENTION According to the present invention, a magnet having toner particles having an average particle diameter of 20 mμ or less and a developer mainly composed of insulating magnetic carrier particles having an average particle diameter of 5 to 50 mμ and a magnet disposed inside the magnet are used. While continuously forming a developer layer by the action of a magnetic force on the developer carrying carrier composed of a sleeve surrounding a magnet, carrying the developer layer to the developing area and a gap between the image carrier and the developer carrying carrier in the developing area. To form an oscillating electric field in the developing area, and the distance between the image carrier and the developer transport carrier in the developing area is larger than the thickness of the developer layer, and And a step of adhering the toner on the image carrier, and attaching the toner to the image carrier. Here, the "average particle diameter" means the average of the diameters of the case particles (numerical average of major axis length and minor axis length).

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view of a developing device used in a developing method according to an embodiment of the present invention. An electrostatic image is formed on the surface of the drum-shaped image carrier 1 composed of a photosensitive material such as Se by a charging / exposure device (not shown), and rotates in the direction of the arrow. The developer carrying carrier 2 provided in the vicinity of the image carrier 1 is composed of a sleeve 2a made of a non-magnetic material such as aluminum and a magnet roll 2b having a plurality of magnetic poles in the circumferential direction. It is usually magnetized to a magnetic flux density of 500 to 1500 gauss. In order to convey the developer D from the developer reservoir 6 to the developing portion A while forming the spikes, the sleeve 2a is fixed, the magnet roll 2b is rotated, and the magnet roll 2b is fixed, and the sleeve is rotated. .. Alternatively, both can be rotated. However, the direction in which the developer D is conveyed is the same as the rotation direction when the sleeve 2a rotates, but the magnet roll 2
When b rotates, the direction is opposite to the direction of rotation. In FIG. 1, when the magnet roll 2b rotates clockwise and the sleeve 2a rotates counterclockwise,
The developer D is conveyed counterclockwise.

In FIG. 2, the magnet roll 2b is fixed, and the sleeve 2a is rotated counterclockwise. At this time, the magnet roll 2b is opposed to the image carrier 1 by the magnetic poles. The magnetic flux density of is larger than the other magnetic flux densities. In order to increase the magnetic flux density of the magnetic poles facing the image carrier 1, as shown in FIG. 3, two magnetic poles having the same or different polarities can be arranged close to each other.

Developer D carried on the peripheral surface of the sleeve 2a.
Is regulated in height by the regulation blade 4, reaches the developing portion A, part of which is sucked by the image carrier 1, and the rest is conveyed on the peripheral surface of the sleeve 2a in the direction of the arrow, and the cleaning blade 5 removes it from the peripheral surface of the sleeve 2a. The stirring screw 7 is used for the developer D in the developer pool 6.
Is provided so as to stir the toner and make the ratio of the toner particles and the carrier particles uniform. When the developer D is developed, many toner particles in the developer D are used and consumed. Therefore, the toner hopper 8 is provided to replenish the toner particles T, and the consumed toner particles T are replenished to the developer pool 6 by rotating the supply roller 9 having a concave portion on the surface. And to prevent fogging,
A power supply 10 for applying a bias voltage to the sleeve 2a via a protection resistor 11 is provided. In addition, this power source 10
Also serves as an oscillating electric field generator for vibrating the developer D in the developing section A between the sleeve 2a and the image carrier.

The above-mentioned electrostatic image developing method is notable in that the magnetic carrier particles have an average particle size of 50 μm.
The average particle diameter of the toner particles is 20 μm or less. In the conventional magnetic brush developing method, the developer D is charged by rubbing, and the developer D is sucked by the Coulomb force with the charged portion of the image carrier 1. Therefore, in order to provide the developer D with a sufficient electric charge for development, there is a limit to making the developer particles fine.

However, in this embodiment, even if the developer D is fine particles, there is no problem as described above. In the present invention, since the oscillating electric field is used, the particles of the developer D are not transferred to the sleeve 2a
Between the image carrier and the image carrier, the visible image by the developer D can be formed on the image carrier 1 without sufficient contact between the developer D and the image carrier 1 as in the conventional magnetic brush developing method. Is formed.

In order to prevent fogging, it is preferable that the developer layer thickness is smaller than the distance between the image carrier and the sleeve, that is, non-contact development is performed. In the non-contact development, since the image carrier is not rubbed with the developer layer, the image carrier is not damaged and the life is long. Further, the moving speed of the developer moves in the same direction as the image carrier or in the opposite direction, and may be the same or faster, but is not limited thereto.

Therefore, it becomes possible to use fine particle carrier particles and toner particles which cannot be used in the conventional magnetic brush developing method. From the above, when the carrier particles used in the present invention are less than 5 μm, particularly less than 4 μm, the magnetization becomes too weak, and when it exceeds 50 μm, the image is not improved, and breakdown or discharge easily occurs, and high voltage cannot be applied. .. On the other hand, the toner particle size is 1
When it is less than μm, it becomes difficult to peel from the carrier even if vibration is applied, and when it exceeds 20 μm, the resolution of the image is lowered. From this point, the toner particle size is preferably 0.5 to 20 μm, and more preferably 1 to 20 μm.
The average charge amount of the toner at this time is 3 to 300 μC /
g is preferable, and 10 to 100 μC / g is particularly preferable.

Since a DC voltage for preventing fogging and an oscillating electric field for vibrating the developer D are applied between the image carrier 1 and the sleeve 2a, the distance between them is a problem. If this interval is too narrow, discharge will occur between the two,
It damages the image carrier and prevents the developer D from passing between them. On the other hand, if the distance between the two is too wide, the counter electrode effect is lowered, recording of sufficient development density is not recorded, and the edge effect is also increased. According to the experiment, the distance between the two is 20.
Desirable results were obtained when the thickness was set to 00 μm or less, and particularly between several tens of μm and 1000 μm.

The direct current bias voltage for preventing fog is normally maintained at a potential higher than that in the non-image area, so a direct current voltage of 50 to 500 V is applied, and in order to vibrate the developer D, 100 to 10 KHZ, Preferably 1-5K
An alternating current of HZ frequency is used. The DC voltage may be smaller than this when the toner has magnetism. When performing reversal development, it goes without saying that a higher DC voltage is applied. The higher the AC voltage value, which depends on the frequency, the more the developer D is vibrated, but on the other hand, fogging is likely to occur and discharge is also likely to occur. When the frequency is increased, the developer D cannot keep up with this change, and the development density and the sharpness are lowered, and the image quality tends to be lowered.

The carrier particles used in the present invention may be the same as the conventional magnetic carrier particles except for the average particle diameter. That is, iron, chromium, nickel, a metal such as cobalt, or a compound or alloy thereof, for example, ferric tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy,
Such as particles of ferromagnetic or paramagnetic material, or the surface of these particles such as styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin Insulating particles such as those coated with fatty acid waxes such as palcytic acid and stearic acid can be used. However, among them, the resistivity is 10 ⁸ Ωcm or more, and particularly preferably 10
Insulating magnetic particles of ¹⁴ Ωcm or more are particularly preferable. When the resistivity is low, when a bias voltage is applied to the developer transport carrier, charges are injected into the carrier particles, and the carrier particles are easily attached to the image carrier, or the bias voltage is not sufficiently applied. The problem arises.

The resistivity is such that the particles are placed in a container having a cross-sectional area of 0.50 cm ² and tapped, and then a load of 1 kg / cm ² is applied to the packed particles so that the load and the bottom electrode are separated from ^each other. It is a value obtained by reading the current value when a voltage that generates an electric field of 1000 V / cm is applied.
The insulating particles are not limited to those having a coating layer of resin or the like on the surface of the magnetic particles, and may be particles having magnetic particles dispersed in the resin.

The carrier particles as described above are manufactured in the same manner as the conventional carrier particles, and the average particle size is selected by the conventionally known average particle size selecting means and used in the present invention. As the toner particles in the present invention, the toner particles obtained by selecting the conventional non-magnetic or magnetic toner particles by the average particle size selecting means can be used. It is preferable that the toner particles are magnetic particles containing magnetic fine particles, and the amount of the magnetic fine particles is 30 wt%.
Those which do not exceed 10 are preferable. When the toner particles contain magnetic particles, the toner particles are affected by the magnetic force of the magnet contained in the developer transport carrier 2, so that the uniform formation of the developer spikes is further improved. In addition, fogging is prevented, and toner particles are less likely to scatter. However, if the amount of the magnetic material contained is too large, the magnetic force between the particles and the carrier particles becomes too large, and it becomes impossible to obtain a sufficient developing density. In addition, it becomes difficult to control triboelectric charging, the toner particles are easily damaged, and the toner particles are easily aggregated with the carrier particles.

For the toner particles as described above, fine particles of resin and further magnetic material as described for the carrier particles are used, and a coloring component such as carbon and, if necessary, a charge control agent and the like are added to the toner particles. It can be produced by a method similar to a known method for producing toner particles. The developer in the present invention is a mixture of the carrier particles and the toner particles as described above in the same proportion as in the conventional two-component developer. A fluidizing agent for improving and a cleaning agent useful for cleaning the surface of the image bearing member are mixed. As the fluidizing agent, colloidal silica, silicon varnish, metal soap, nonionic surface active agent or the like can be used, and as the cleaning agent, fatty acid metal salt, organic group-substituted silicon or fluorine surface active agent or the like can be used. You can

Development is carried out according to the above-mentioned developer D and the developing conditions. When the developer D attracted to the charging portion of the image carrier 1 is only toner particles, both the toner particles and carrier particles are attracted. In some cases, a visible image is formed on the image bearing member 1, and a desired result can be obtained by appropriately selecting both. In order to develop only with toner particles, the carrier particles must remain on the peripheral surface of the developer carrier 2, and only the toner particles must vibrate between the image carrier 1 and the developer carrier 2 due to the oscillating electric field. I won't. Therefore, the toner particles overcome the adhesion forces such as Coulomb force and Van der Waals force with the carrier particles and separate from the carrier particles, so that the high oscillating electric field, the high charge amount of the toner particles, the developer carrier 2 and the image carrier. In order to prevent the magnetic carrier from vibrating between the magnet roll 1 and the magnetic carrier 1, the magnet roll 2b is required to have a strong holding force. In order that the carrier particles do not vibrate together with the toner particles, the particle size of the carrier particles is larger than that of the toner particles, the magnetic binding force acting on the carrier particles is larger than the electrostatic force for moving to the image carrier, the toner particles It is desirable that the charge amount of is larger than 1 to 3 μc / g (preferably 3 to 300 μc / g). Especially when the particle size is small, a high charge amount is required. When a visible image is formed on the image bearing member 1 only by toner particles, the surface of the image bearing member 1 is not damaged by the carrier particles, and even if there is a pre-developed visible image on the image bearing member 1, a new image is newly formed on that portion. In addition, it has an advantage that a visible image can be formed on the image carrier 1 in double. In order to form a visible image on the image carrier 1 with both the toner particles and the carrier particles, the toner particles overcome the adhesive force with the carrier particles and do not need to be separated, so that the toner particles and the carrier particles are required. The conditions are not strict. Since the carrier particles may vibrate between the image carrier 1 and the developer carrying carrier 2 by the oscillating electric field, the carrier particle size may be smaller than the toner particle size, and the magnetic binding force acting on the carrier particles is weak. The toner particles may have a small charge amount. From the above, compared with the above, carrier particles and toner particles having a small particle diameter can be used. When developed with only toner particles, the carrier particles have an average particle diameter of 10 μm and the toner particles have an average particle diameter of 5 μm.
If it is less than μm, it becomes difficult to form a high-quality visible image, but when developed with both toner particles and carrier particles, the average particle diameter of the carrier particles is 5 μm, and the average particle diameter of the toner particles is A high-quality image was formed even when the thickness was about 1 μm. Further, the vibration of the carrier particles also has an effect of preventing aggregation of the toner particles.

In the vibration range of the developer, it is effective to apply a magnetic field to change it temporally or spatially. Such visible image formation is possible by non-contact development. Development with a magnetic brush damages the image carrier 1. Under the development conditions described above,
The results of experiments conducted by the inventor are shown below. (A) The carrier particles have an average particle size of 20 μm and a magnetization of 50.
Using spherical ferrite particles having an emu / g and a resistivity of 10 ¹⁰ Ωcm, 100 parts by weight of styrene and acrylic resin (Haimer up110 manufactured by Sanyo Kasei), 10 parts by weight of carbon black (MA-100 manufactured by Mitsubishi Kasei) and nigrosine are used as toner particles. Under the condition that the toner particle ratio of the developer D in the developer pool 6 is 10 wt% with respect to the carrier particles using the apparatus shown in FIG. It was developed.

In this case, the image carrier 1 is a CdS photosensitive member, the peripheral speed is 180 mm / sec, the maximum potential of the electrostatic image formed on the image carrier 1 is -500 V, and the outer diameter of the sleeve 2a is 30.
mm, rotation speed 100 rpm, magnet roll 2b
The magnetic flux density of the N and S magnetic poles is 500 gauss, the rotation speed is 1000 rpm, and the developer layer thickness in the developing section is 0.2 m.
m, the gap between the sleeve 2a and the image carrier 1 is 0.3 mm, that is, 300 μm, and the bias voltage applied to the sleeve 2a is a DC voltage component of −250 V and an AC voltage component of 1.5 KHZ.
The non-contact development was set to 400V.

Development is carried out under the above conditions, and the result is printed on plain paper.
To a heat roller fixing device with a surface temperature of 140 ° C.
After fixing the image, the resulting image on the recording paper has an edge effect.
Extremely clear with no fog and high density
And then I got 50,000 sheets of recording paper from the beginning to the end
I was able to obtain a stable and stable image. It
The bias voltage applied to the sleeve 2a to DC
Recording under the same conditions as above except that only the voltage component was used
As a result, an unclear image with low density was obtained. Well
In addition, the gap between the sleeve 2a and the image carrier 1 is 3.0 mm,
That is, the thickness is 3000 μm, and the developer layer thickness in the developing section is 0.7.
The recording was obtained under the above conditions except for the magnetic brush development of mm.
The result is that the image has an edge effect and the density is low.
there were. (B) Carrier particles have an average particle size of 15 μm and a magnetization of 70e
mu / g, resistivity 10 ¹⁴Resin coating of Ωcm or more
Toner particles using insulated spherical ferrite particles
As shown in FIG. 2, non-magnetic particles having an average particle size of 5 μm are used for
Toner particles of the developer D in the developer pool 6 by the device
Develop under the condition that the ratio is 5 wt% with respect to carrier particles
I went.

In this case, the conditions of the image carrier 1 are the same as those in the experimental example A, the outer diameter of the sleeve 2a is 30 mm, the rotation speed is 150 rpm, and the magnetic flux velocity of the magnetic pole facing the developing portion A of the magnet roll 2b is 1200. Gaussian, developer layer in developing area 0.3 mm, sleeve 2a and image carrier 1
0.4mm, ie 400μm, sleeve 2a
The non-contact development was carried out by applying a bias voltage of −100 V to a DC voltage component of 3 KHZ and 1200 V as an AC voltage component.

After developing under the above conditions, transferring it to plain paper and fixing it through a heat roller fixing device having a surface temperature of 140 ° C., the resulting image on the recording paper is free from edge effects and fog. There was no image and the density was extremely high, and the image was very clear. Subsequently, 50,000 sheets of recording paper were obtained, but it was possible to obtain a stable image from the beginning to the end.

Further, a recording paper was obtained under the same conditions as described above except that the bias voltage applied to the sleeve 2a was only a DC voltage component, but an image slightly poor in image density and sharpness was obtained. On the other hand, recording is performed under the same conditions as above except for the magnetic brush development in which the gap between the sleeve 2a and the image carrier 1 is 3.0 mm, that is, 3000 μm, and the developer layer thickness in the developing section is 0.7 mm. As a result of obtaining the paper, the edge effect was observed in the image and the density was low. (C) Carrier particles containing fine ferrite in resin 50w
t% dispersed average particle diameter 10 μm, magnetization 30 emu /
g, using a resistivity of 10 ¹⁴ [Omega] cm or more resin dispersion based carrier particles, styrene toner particles, acrylic resin (manufactured by Sanyo Chemical Industries, Ltd. Mannheimer up110) 100 parts by weight of carbon black (Mitsubishi Chemical Industries Ltd. MA-100) 10 parts by weight, By using magnetic particles having an average particle diameter of 3 μm and composed of 5 parts by weight of nigrosine and 5 parts by weight of fine ferrite particles, the toner particle ratio of the developer D in the developer pool 6 to the carrier particles is measured by the apparatus shown in FIG. Development was carried out under the condition that the total amount was 10 wt%.

In this case, the image carrier 1 is a CdS photosensitive member, the peripheral speed is 180 mm / sec, the maximum potential of the electrostatic image formed on the image carrier 1 is -500 V, and the outer diameter 3 of the sleeve 2a.
0 mm, its rotation speed 100 rpm, magnet roll 2
The magnetic flux density of the N and S magnetic poles of b is 500 gauss, the rotation speed is 1000 rpm, and the developer layer thickness in the developing section is 0.2 m.
m, the gap between the sleeve 2a and the image carrier 1 is 0.3 mm, that is, 300 μm, and the bias voltage applied to the sleeve 2a is a DC voltage component of −250 V and an AC voltage component of 1.5 KHZ.
The non-contact development was set to 400V.

After development under the above conditions, the image was transferred to plain paper and passed through a heat roller fixing device having a surface temperature of 140 ° C. to fix the image. There was no image and the density was extremely high, and it was very clear. Subsequently, 50,000 sheets of recording paper were obtained, but a stable and unchanging image from the beginning to the end could be obtained. On the other hand, as a result of obtaining the recording paper under the same conditions as described above except that the bias voltage applied to the sleeve 2a was only the DC voltage component, an unclear image with low density was obtained.
In addition, the gap between the sleeve 2a and the image carrier 1 is 3.0 m.
m, that is, 3000 μm, and a recording paper was obtained under the same conditions as above except for the magnetic brush development in which the developer layer thickness in the developing section was 0.7 mm. It was low. (D) Carrier particles have an average particle size of 4 μm and a magnetization of 70 em
Using resin-coated insulating spherical ferrite particles having a u / g and a resistivity of 10 ¹⁴ Ωcm or more, and non-magnetic particles having an average particle size of 5 μm as toner particles, a developer pool 6 was formed by the apparatus shown in FIG. Development was performed under the condition that the toner particle ratio of the developer D in 5 was 5 wt% with respect to the carrier particles.

In this case, the conditions of the image carrier 1 are the same as those in the experimental example A, the outer diameter of the sleeve 2a is 30 mm, the rotation speed is 150 rpm, and the magnetic flux velocity of the magnetic poles facing the developing area A of the magnet roll 2b is 1200. Gauss, the magnetic flux density between the magnetic poles is 800 gauss, the developer layer in the developing area is 0.3 mm, and the gap between the sleeve 2a and the image carrier 1 is 0.
4 mm, that is, 400 μm, the bias voltage applied to the sleeve 2a is DC voltage component −100 V, AC voltage component 3 K
The non-contact development was HZ and 1200V.

After developing under the above conditions, transferring it to plain paper and fixing it by passing it through a heat roller fixing device having a surface temperature of 140 ° C., the resulting image on the recording paper is free from edge effects and fog. There was no image and the density was extremely high, and it was very clear. Subsequently, 50,000 sheets of recording paper were obtained, but a stable and unchanging image from the beginning to the end could be obtained.

Further, a recording paper was obtained under the same conditions as described above except that the bias voltage applied to the sleeve 2a was only a DC voltage component, but an image slightly poor in image density and sharpness was obtained. On the other hand, the gap between the sleeve 2a and the image carrier 1 is 3.0 mm, that is, 3000 μm,
As a result of obtaining a recording paper under the same conditions as above except that the developer layer thickness in the developing section was 0.7 mm, the edge effect was observed in the image and the density was low.

Since no vibration of the carrier particles was observed in Experiments A and B, it is considered that the carrier particles did not substantially vibrate under the conditions of A and B. FIG. 4 and FIG. 5 show the frequency of the AC voltage for generating the oscillating electric field and the result when the voltage was changed under the developing conditions in which the good results described in Experiments A and B were obtained. It is a figure. In the figure, the part shaded with horizontal lines is the range in which fogging is observed, the part shaded with vertical lines is the range in which dielectric breakdown occurs due to discharge, and the part shaded with diagonal lines is the range in which image deterioration occurs The non-treated portion is an appropriate range where a high-quality visible image is formed, and the low-frequency region shaded with dots is a range where the frequency is low and uneven development is observed.

6 and 7 show the results when the voltage and frequency of the alternating current for generating the oscillating electric field were changed under the condition that good results were obtained in Experiments C and D.
As is clear from FIGS. 6 and 7, the results of experiments C and D were similar to those of experiments A and B. In Experiments C and D, when the vibration of the carrier particles was observed, the vibration occurred in the upper range indicated by the broken line in the proper range, and did not occur in the lower range. The recorded image was excellent in image density, gradation and resolution in the range above the broken line even in the proper range. The waveform of the AC voltage component in the present invention is not limited to a sine wave, and may be a rectangular wave or a triangular wave. In addition, if the toner in the two-component developer has magnetism, it goes without saying that the magnetic latent image can be visualized under the same developing conditions.

[0040]

[Effect] In the conventional magnetic brush developing method, when the two-component developer was used, the toner particles and the carrier particles could not be atomized, so that high-quality image recording could not be performed. However, according to the electrostatic image developing method of the present invention, the average particle size of the toner particles is 20 μm or less and the average particle size of the carrier particles is 5 to 50 μm under the condition of applying vibration.
In the developing step, an electric field due to a bias voltage is formed between the surface of the developer carrying carrier and the image carrier. Due to this electric field, an electric force acts not only on the toner on the surface of the developer layer but also on the entire toner in the developer layer. As a result, the toner in the developer layer is efficiently used and a high-density toner image is obtained.

Further, since the non-contact development is used, it is possible to obtain a recording having a sufficient image density and gradation and excellent resolution. Further, since the developer is a two-component system (or more may be used), the toner charge is more stable and aggregation is less likely to occur as compared with a one-component system.

[Brief description of drawings]

FIG. 1 is a schematic view of a developing device used in an embodiment of the present invention.

FIG. 2 is a schematic view of a developing device used in an embodiment of the present invention.

FIG. 3 is a schematic view of a developing device used in an embodiment of the present invention.

FIG. 4 is a diagram showing the results obtained according to the example of the present invention.

FIG. 5 is a diagram showing results obtained according to an example of the present invention.

FIG. 6 is a diagram showing the results obtained according to the example of the present invention.

FIG. 7 is a diagram showing the results obtained according to the example of the present invention.

[Explanation of symbols]

 1 image carrier 2 developer carrier 2a sleeve 2b magnet roll 4 regulating blade 5 cleaning blade D developer T toner

Claims (1)

[Claims] 1. A magnet in which a developer mainly containing toner particles having an average particle size of 20 mμ or less and insulating magnetic carrier particles having an average particle size of 5 to 50 mμ is arranged, and a sleeve surrounding the magnet. While continuously forming a developer layer on the developer transport carrier by the action of magnetic force, transporting the developer layer to the developing region and forming the development region as a gap between the image carrier and the developer transport carrier, An oscillating electric field is formed in the area, and the distance between the image carrier and the developer carrier in the developing area is set to be larger than the thickness of the developer layer so that the toner in the developer is carried in the developing area. Developing method comprising the steps of moving and attaching the body